Evidence that intragenic recombination contributes to allelic diversity ofthe S-RNase gene at the self-incompatibility (S) locus in Petunia inflata

Citation
X. Wang et al., Evidence that intragenic recombination contributes to allelic diversity ofthe S-RNase gene at the self-incompatibility (S) locus in Petunia inflata, PLANT PHYSL, 125(2), 2001, pp. 1012-1022
Citations number
41
Categorie Soggetti
Plant Sciences","Animal & Plant Sciences
Journal title
PLANT PHYSIOLOGY
ISSN journal
00320889 → ACNP
Volume
125
Issue
2
Year of publication
2001
Pages
1012 - 1022
Database
ISI
SICI code
0032-0889(200102)125:2<1012:ETIRCT>2.0.ZU;2-0
Abstract
For Solanaceae type self-incompatibility, discrimination between self and n onself pollen by the pistil is controlled by the highly polymorphic S-RNase gene. To date, the mechanism generating the allelic diversity of this gene is largely unknown. Natural populations offer a good opportunity to addres s this question because they likely contain different alleles that share re cent common progenitors. We identified 19 S haplotypes from a natural popul ation of Petunin inflata in Argentina, used reverse transcriptase-polymeras e chain reaction to obtain cDNAs for 15 alleles of the S-RNase gene, and se quenced all the cDNAs. Phylogenetic studies revealed that five of these all eles and two previously identified alleles form a major clade, and that the 5' region of S-19 allele was derived from an ancestor allele closely relat ed to S-2, whereas its 3' region was derived from an ancestor allele closel y related to S-8. A similar evolutionary relationship was found among S-3, S-12, and S-15 alleles. These findings suggest that intragenic recombinatio n contributed to the generation of the allelic diversity of the S-RNase gen e. Two additional findings emerged from the sequence comparisons. First, th e nucleotide sequence of the S-1 allele identified in this work is complete ly identical to that of the previously identified S-1 allele of a different origin. Second, in the two hypervariable regions HVa and HVb, thought to b e involved in determining S allele specificity, S-6 and S-9 alleles differ only by four nucleotides, all in HVb, resulting in two amino acid differenc es. The implications of these findings are discussed.